Select the oval object as fast as you can without making mistakes!

Help us understand better how humans detect objects correctly under different conditions.

You will see two marble blocks. On one of the blocks there will always be an oval object like the ones indicated by the red arrow below (the objects on the other block will change on every trial, but they will never be an oval). Note that the size of all the objects will change on every trial; your task is to identify the oval object regardless of its size.

Press "1" when the Oval Object
is on Block 1

example_image_1 example_image_4

Press "2" when the Oval Object
is on Block 2

example_image_3 example_image_2

Your task is to press "1" or "2" on your keyboard to indicate the number of the block where the oval object is.

You should do this as quickly as you can without making mistakes. You'll have up to 2 seconds to respond. We'll let you know if you were too slow. Please mind that your responses will be useful only if at least 80% of them are correct. We will give you feedback on each trial (green = correct, red = wrong).

Note that the This HIT is short (less than 6 minutes), so please try to stay focused. It's important that you pay attention to the screen all the time.

Make sure your browser window is maximized. You must be on a laptop or desktop computer to participate in this HIT (no cellphones or tablets). Click "Start Experiment" to begin with a few practice trials.

By completing this survey or questionnaire, you are consenting to be in this research study. Your participation is voluntary and you can stop at any time.

Please wait while your browser finishes a few things behind the scenes.
Start Experiment
You're done with practice!

If you haven't already, please maximize your browser window.

Press spacebar to start the experiment.

Good job! Sometimes the images we use fail to display correctly. We just want to make sure they were correctly displayed for you. Before you submit, please answer the following four questions:


What is this?

A circular object
An oval object


What is this?

A circular object
An oval object


What is this?

A circular object
An oval object


What is this?

A circular object
An oval object

Show submit button
All done! You can now submit the HIT. Thank you!

Please feel free to leave any comments below about how the experiment went.